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Vol. 94 No. 6 December 2002
Apical periodontitis: A very prevalent problem
Apical periodontitis, an inflammatory process around
the apex of a tooth root, is primarily a sequel to
microbial infection of the pulp space of teeth and is
a remarkably widespread problem.1 The prevalence
of apical periodontitis increases with age: by 50
years of age, 1 in 2 individuals will experience the
disease.2 In individuals over 60 years old, the prevalence of apical periodontitis rises to 62%.2 The
clinical management of apical periodontitis involves
infection control by root canal treatment, which is
the only viable alternative to the unsatisfactory option of tooth loss. On the basis of an average number
of 2.2 root fillings per adult,3 it can be estimated
from census data that there are 25 million root filled
teeth in Australia and more than 420 million root
filled teeth in the US. In the year 1990, an estimated
14 million root canal treatments were performed in
the US alone.4
The magnitude of the problem does not seem to
have been fully appreciated, and therefore apical
periodontitis has not attracted the attention deserved
by such a common disease. Another reason that
apical periodontitis may not have received a greater
degree of interest is that the success rate of treatment
has generally been regarded as high, of the order of
87%.2 This figure applies to endodontic treatment
done in specialist practice where a higher expertise is
likely to result in a better technical standard of
treatment, whereas the success rate in general practice is of the order of 72%.2 However, when the
failure rate is measured relative to the prevalence of
root canal treatment, the full dimension of the problem becomes apparent. When a conservative failure
rate of 13% for root canal treatment in the average
population is assumed, it can be estimated that there
are 3.3 million failed root canal treatments in Australia and 54 million in the US; taking the greater
failure rate for treatment in general practice, the
figures could be as high as 7 million and 117 million,
respectively. When these numbers are multiplied by
the cost of endodontic retreatment and crown or
restoration replacement, the cumulative economic
impact is in the order of billions of dollars.
In recent years there has been a trend toward
focusing on the technical aspects of mechanical instrumentation of the root canal as a measure of
success of endodontic treatment. Although the mechanical elements of treatment undoubtedly deserve
attention, a critical evaluation of relevant factors
involved in the etiology of endodontic failure is more
likely to yield meaningful information and, ultimately, rational treatment solutions. Sound clinical
treatment must be based on a clear understanding of
the causative factors in the disease process, so that
intelligent and logical solutions can be applied to
address the problem. For apical periodontitis, the
essential role of microbial infection is well recognized as the critical etiological factor. Therefore,
endodontic treatment is fundamentally the clinical
management of a microbiological problem.
It is logical, then, that the principal treatment objective is elimination of bacteria and exclusion of further
infection from the root canal. A clean, infection-free
canal can best be accomplished by mechanical instrumentation in the presence of antibacterial irrigation
followed by an antimicrobial intracanal dressing, which
should in most cases provide predictable elimination of
Although the method of root filling with guttapercha was first described more than 135 years ago,5
it is astonishing that relatively modest progress has
been made in defining the relative contribution of the
root filling in the overall antimicrobial approach to
root canal treatment. The idea that fluids percolating
into an empty “dead” space might break down and be
the cause of apical periodontitis originated as early
as the 1930s,6 but vestiges of the concept linger to
the present day despite evidence demonstrating the
fallacy of the idea.7,8 The hypothesis that the “dead”
space was a prime cause of apical periodontitis was
propagated further during the mid-1950s and 1960s
when the “Washington study,” taken together with an
652 Figdor
apical leakage study,9,10 purported to confirm that
most failures are caused by poor root canal obturation. A critical flaw in the hypothesis was that it
failed to take into account the essential role of bacteria in the pathogenesis of apical periodontitis.
If the canal is free of infection at the time of
obturation, there is a higher chance of success.11,12
Advanced bacteriological techniques have recently
been used to show that when bacteria persist in the
canal at the time of root filling, there is a higher risk
that the treatment will fail.13 How high this risk will
be depends on the quality of the root filling. In some
of these cases the bacteria will die from the agents
used in the root filling, and in other cases they will be
entombed or lose access to nutritional material and
die. But in all cases where viable bacteria remain in
the root canal, there is a constant risk that they may
continue to maintain a periapical inflammation.
During the latter part of the 20th century, a large
number of journal publications have been devoted to
variations of root filling methods with proponents for
different techniques, but this has not led to a more
sophisticated scientific approach to root canal treatment. That is not to say that a well-obturated root
canal is inconsequential—it is undoubtedly an important component of good clinical treatment— but it
ought to be viewed in relation to how it supplements
the overall antimicrobial strategy. Recent studies
have shown that obturation of infected canals may
result in periapical tissue healing in a proportion of
cases, but that optimal success is achieved when the
canal has been rendered free of recoverable bacteria
before root filling.13-15
It is clear from this discussion that there are broad
health, social, and economic consequences of failure
of endodontic treatment and potentially significant
benefits individually and collectively if it were possible to reduce the proportion of endodontic failures.
More research activity should be directed to where it
can be of most benefit, which means a greater focus
on the primary problem—why treatment fails and
what can be done to address it. Although much more
knowledge is required, there is already a substantial
December 2002
source of information on improved treatment procedures. This information needs to be applied in the
educational process and implemented at all levels.
David Figdor, MDSc, FRACDS,
Dip Endo, FPFA, PhD
Senior Fellow, School of Dental Science,
University of Melbourne
Melbourne, Australia
1. Figdor D. Microbial aetiology of endodontic treatment failure
and pathogenic properties of selected species. Umeå University
Odontological Dissertations No. 79. Umeå (Sweden): Umeå University; 2002.
2. Eriksen HM. Epidemiology of apical periodontitis. In: D Ørstavik, TR Pitt Ford, editors. Essential Endodontology. Prevention
and treatment of apical periodontitis. London: Blackwell Science; 1998. p. 179-91.
3. Eriksen HM. Endodontology— epidemiologic considerations.
Endod Dent Traumatol 1991;7:189-95.
4. American Dental Association. 1990 Survey of Dental Services
Rendered. Chicago: American Dental Association; 1994.
5. Cruse WP, Bellizzi R. A historic review of endodontics, 16891963, part 1. J Endod 1980;6:495-9.
6. Rickert UG, Dixon CM. The controlling of root surgery. Transactions of the Eighth International Dental Congress, 1931;15.
7. Torneck CD. Reaction of rat connective tissue to polythylene tube
implants. Part I. Oral Surg Oral Med Oral Pathol 1966;21:379-87.
8. Torneck CD. Reaction of rat connective tissue to polyethylene
tube implants. Part II. Oral Surg Oral Med Oral Pathol 1967;
9. Ingle JI, Glick DH. Modern endodontic therapy. In: JI Ingle editor.
Endodontics. 1st ed. Philadelphia:Lea & Febiger;1965. p. 25-77.
10. Dow PR, Ingle JI. Isotope determination of root canal failure.
Oral Surg Oral Med Oral Pathol 1955;8;1100-4.
11. Engstrom B, Hård af Segerstad L, Ramström G, Frostell G.
Correlation of positive cultures with the prognosis for root canal
treatment. Odont Revy 1964;15:257-70.
12. Heling B, Shapira J. Roentgenologic and clinical evaluation of
endodontically treated teeth, with or without negative culture.
Quintessence Int 1978; 9:79-84.
13. Sjögren U, Figdor D, Persson S, Sundqvist G. Influence of
infection at the time of root filling on the outcome of endodontic
treatment of teeth with apical periodontitis. Int Endod J 1997;
14. Katebzadeh N, Hupp J, Trope M. Histological periapical repair
after obturation of infected root canals in dogs. J Endod 1999;
15. Katebzadeh N, Sigurdsson A, Trope M. Radiographic evaluation
of periapical healing after obturation of infected root canals: an
in vivo study. Int Endod J 2000;33:60-6.